High sample rate dPES to improve contact detection signal to noise ratio

Abstract

Using a high sample rate dPES, together with pulsed heater and lock-in technique, to improve dPES SNR for contact detection between the head and media surface. Steps of powering a transducing head actuator with pulsed input signal at a select data track offset from a previously-written to data track of the storage medium, where the pulsed input signal has select amplitude and duty cycle to simulate a response signal, and further locking in an amplitude with respect to the heater frequency, can lead to a determination of level of heater power for initiating contact between the transducing head and the storage medium.

What is claimed is: 
     
       1. A method of detecting initial contact between a transducing head and a storage medium, the method comprising:
 providing a pulsed input signal to an actuator of the transducing head, wherein a sampling frequency of the input signal is at least four times higher than a heater frequency; 
 sampling amplitudes of the input signal; 
 determining a lock-in amplitude from the sampled amplitudes, wherein the lock-in amplitude is determined through use of an algorithm with respect to the response signal at the sampled amplitudes; 
 generating a curve of the lock-in amplitude against varied heater power; and 
 determining a turning point of the curve. 
 
     
     
       2. The method of  claim 1  wherein the turning point corresponds to level of heater power for providing the initial contact between the transducing head and the storage medium. 
     
     
       3. The method of  claim 1 , wherein the actuator comprises a heater, the method further comprising steps of:
 performing a cross scan of a surface of the storage medium with regard to read back intensity in relation to a single data track; 
 performing at single data track steps of:
 providing a pulsed input signal to the heater of the transducing head, 
 sampling amplitudes of the input signal at a frequency higher than frequency of the heater of the transducing head, 
 determining a lock-in amplitude from the sampled amplitudes so as to limit response signal to noise not attributed from position of the heater, and 
 generating a curve of the lock-in amplitude against varied heater power; and 
 
 differentiating the curve generated for the select data track and the curve generated for the single data track in determining the turning point. 
 
     
     
       4. The method of  claim 3  wherein the read back intensity is measured for varied radius of the storage medium from the single data track during the cross scan. 
     
     
       5. The method of  claim 3  wherein the read back intensity at the select data track is less than the read back intensity at the single data track, enabling the response signal at the select data track to be simulated from full heater stroke. 
     
     
       6. The method of  claim 1  further comprising a step of taking a derivative of the curve, resulting in a further curve that is near linear with the turning point being more distinguishable on the further curve. 
     
     
       7. The method of  claim 1  wherein a sampling frequency of the input signal is at least 1 MHz. 
     
     
       8. The method of  claim 1  wherein the algorithm processes both noise and signal components of the response signal, the response signal having both AC and DC components, and wherein the AC component is subsequently removed. 
     
     
       9. The method of  claim 8  wherein the AC component is removed via a low pass filter. 
     
     
       10. The method of  claim 8  wherein the AC component is removed via a digital locking amplifier. 
     
     
       11. A method of determining heater power requisite to initiate contact between a transducing head and a storage medium, the method comprising:
 powering a heater of the transducing head with pulsed input signal at a select data track of the storage medium, the pulsed input signal having select amplitude and duty cycle to simulate a response signal at the select data track, the select data track being offset from a single data track of the storage medium previously written to; 
 sampling amplitudes of the input signal at a frequency higher than frequency of the heater; 
 determining a lock-in amplitude from the sampled amplitudes; 
 generating a curve of the lock-in amplitude against varied heater power; and 
 determining a turning point of the curve. 
 
     
     
       12. The method of  claim 11  further comprising steps of:
 performing a cross scan of a surface of the storage medium with regard to read back intensity in relation to the single data track; 
 performing at the single data track steps of:
 powering the heater of the transducing head with pulsed input signal, 
 sampling amplitudes of the input signal at a frequency higher than frequency of the heater of the transducing head, 
 determining a lock-in amplitude from the sampled amplitudes so as to limit response signal to noise not attributed from position of the heater, and 
 generating a curve of the lock-in amplitude against varied heater power; and 
 
 differentiating the curve generated for the select data track and the curve generated for the single data track in determining the turning point. 
 
     
     
       13. The method of  claim 12  wherein the read back intensity at the select data track is less than the read back intensity at the single data track, enabling the response signal at the select data track to be simulated from full heater stroke. 
     
     
       14. The method of  claim 11  further comprising a step of taking a derivative of the curve, resulting in a further curve that is near linear with the turning point being more distinguishable on the further curve. 
     
     
       15. The method of  claim 11  wherein the lock-in amplitude is determined through use of an algorithm with respect to the response signal at the sampled amplitudes. 
     
     
       16. The method of  claim 15  wherein the algorithm processes both noise and signal components of the response signal, the response signal having both AC and DC components, and wherein the AC component is subsequently removed. 
     
     
       17. The method of  claim 11 , wherein the pulsed input signal simulates a response signal with modulated friction.